1. Field of the Invention
The invention relates to an amplifier and a feedback unit for reducing an offset fraction in the output signal of the amplifier.
2. Description of the State of the Art
In the context of amplifiers a problem can arise in that an input offset of the amplifier (and also an offset of the input signal) can be amplified at the same time by the amplifier so that the output signal of the amplifier comprises an undesirable steady component. This problem is encountered in particular in the case of amplifiers that are designed for amplifying high-frequency signal components. In such broadband amplifiers the transistors have to be of very small dimensions so that frequency components, for example in the gigahertz range, can be amplified. This relatively small dimensioning of the transistors results in significant fluctuations in the transistor threshold voltages, and consequently a significant input offset results. When this input offset is then amplified at the same time, the steady component obtained at the output can easily reach the magnitude of the dynamic range. For example an input offset of up to 10 mV at an amplification of approximately 30 dB results in a steady component of approximately 300 mV at the output, which corresponds to roughly half of the dynamic range.